1. Field of the Invention
This invention relates generally to the field of surgical devices, and, more particularly, to an indwelling catheter for draining the urinary bladder, with the proximal part of the catheter being self-retaining in a manner that minimizes bladder irritation and leaves essentially no residual urine in the bladder.
2. Prior Art
A urinary bladder drainage tube is used in certain patients who have had major surgery and/or trauma, or in any patient unable to urinate. There are many causes of an inability to urinate, these causes differing with age and sex. For example, a small child may not be able to urinate because of some congenital abnormality that obstructs the bladder neck or urethra. In females, inability to urinate occurs in neurological diseases, or after major abdominal or pelvic surgery.
It is often desirable to drain the bladder continuously after major surgery or trauma, at least for the purposes of monitoring renal function by measuring the hourly urine output. It is desirable to continuously drain the bladder by an indwelling urinary catheter in those medical conditions in which the measurement of hourly urine output is important for the timely and appropriate care and well being of the patient.
It is further important to drain the bladder by an indwelling urinary catheter after prostate or bladder surgery. Diverting the urine and blood promotes healing and helps to prevent blood clots from accumulating in the bladder, thus potentially causing more bleeding and severe pain.
Continuous bladder irrigation is used following certain bladder or prostate surgeries. This is achieved by instilling fluid continuously into the bladder and simultaneously draining the bladder using a type of urinary catheter called a three-way catheter. One port serves as a fluid injection port into the bladder, while the second port is for continuous drainage of the bladder contents into a urine collection bag. The third port incorporates a valve mechanism by which the catheter balloon is reversibly inflated once positioned inside the bladder to keep the tip of the indwelling urinary catheter in place.
In certain patients, the bladder must be drained for many years, as in some debilitated patients, or those with neurological or spinal cord lesions. If the bladder is not adequately drained the pressure in the bladder increases and the pressure likewise increases in the ureters and kidneys, causing the kidneys to become obstructed. Unrelieved bilateral kidney obstruction may lead to renal failure within a few weeks. Therefore, the use of an indwelling urinary catheter is quite important, and can be life saving both in acute and chronic or long-term settings.
There are some serious drawbacks to the standard indwelling urinary catheters now available. The widely-used Foley catheter has a retention balloon that is inflated when positioned inside the bladder and which rests on the most sensitive areas of the bladder, the trigone and bladder neck areas. The size of this retention balloon varies between 5 and 30 cc's and the general practice now is to inflate the catheter balloon with 10 to 30 ml's of water. The weight of the Foley catheter balloon when filled with water ranges between 10 and 30 grams. This weight often causes pain and bladder irritation, generally known among urologists to provoke very painful bladder spasms.
In addition to its weight, the balloon is situated below the drainage opening of the Foley catheter, so residual urine inevitably collects in the bladder around the balloon. The amount of residual urine that collects around the balloon averages between 3 and 10 mls. The presence of residual urine promotes infection and is a further source of bladder irritation. Furthermore, in rare instances, the balloon may be inadvertently inflated inside of the urethra, causing trauma to the urethra and resulting thereby in pain, bleeding and possible stricture formation within the urethra.
Pre-grant publication 2002/0143292 is directed to a conformable balloonless catheter system, an indwelling catheter with a proximal end that includes a retention portion made to expand without having to be inflated. One of the preferred embodiments allows for at least one slit on an upper side of the catheter tube and a head member that when pulled down by a stylette moving longitudinally inside the catheter causes a bulged wing portion that holds the catheter safely and painlessly within the bladder. As seen in FIGS. 11-14, traction on the stylette 50 causes the slit walls 68 to move radially as the proximal tip is pulled distally, thereby causing the catheter tip to assume a mushroom-type retention form while providing apertures for the drainage of urine. This is a complex catheter system that uses a stylet introducer with a a magnetic cycling valve and a screwing mechanism to open the retaining element. The use of a stylet to introduce the catheter into the urinary tract and bladder is dangerous and potentially traumatizing. The urethra is S-shaped when the penis is flaccid and becomes L-shaped when the penis is stretched or when erect; using a straight wire stylet thus could perforate the urethral wall, a most serious complication. Furthermore, catheters are usually inserted by nurses but prevailing standards of care and insurance constraints do not allow nurses to use a stylet to insert a urinary drainage catheter because of the associated risks of urethral trauma and/or perforation. It is not practicable to have a urinary catheter system that relies on a stylet for placement since nurses, who are the healthcare providers most widely relied on for catheter insertions, are not permitted to use them.
U.S. Pat. No. 4,349,029 is directed to a balloon catheter drainage system, a catheterization apparatus with a retention balloon to be expanded when the proximal end of the catheter is in the bladder. The balloon, when expanded, comprises a plurality of wings or loops that function in cooperation with at least one opening or aperture which communicates the interior bore or lumen of the catheter with the bladder so that the bladder wall cannot occlude the aperture. The design of this Patent system is such that substantially little or no residual urine remains in the bladder. With reference to FIGS. 2-6, the openings 16 are both above and below the inflatable arms of the retention element of the catheter. Furthermore, the reversibly inflatable anchoring element at the catheter end has something of a steering wheel-type shape which prevents the bladder walls from obstructing the apertures, and when inflated accomplishes the retention of the catheter within the bladder. The ring 22 is attached to the catheter shaft 17 by a plurality of spokes 23. As such, this reference Patent system includes inflatable horizontal elements as well as draining apertures, both distal and proximal to that reversibly expandable element. Second and third embodiments are reflected in FIGS. 5 and 7, where the balloon 69 has three individual loops 71 that are reversibly fillable with fluid for expansion, thereby both exposing and opening the drainage apertures 67 and 83 to accomplish the emptying of the bladder with minimal or no residual volume. In contradistinction to the present subject Patent system, this catheter system replaces the stylet with a second catheter so that the retaining part remains closed; once the retaining part is inside the bladder then the second catheter, acting as a soft stylet, is withdrawn. This system is meant to be a totally closed system to obviate the chance of catheter-related infections. Furthermore, unlike the present subject patent application, the retaining parts are inflatable. The structure of this system is complex and very expensive to manufacture.
U.S. Pat. No. 2,649,092 is directed to a catheter very similar to the present urinary catheter system. A wire or flexible member 30 is fixed to the inside proximal tip 28 and, when pulled, causes the catheter's closed end 14 to foreshorten, thereby radially displacing the “outwardly projecting portions 20” to an open configuration seen in FIG. 3-6. In contradistinction to the present subject catheter system, this reference system needs a stylet at least for its insertion. “A stylet (not shown) is inserted in tubular member 12 and its forward end is brought to bear against the rearward end of plug 24. The stylet is moved forwardly with respect to the tubular member, causing portions 20 to be extended due to their flexibility, and the catheter and stylet are inserted in a body passage to the desired location, such as into the bladder. The stylet is then removed, allowing the parts of the cathter to return to the position shown in FIG. 1.” (Column 3, lines 22-32) The present invention does not use a stylet, for reasons already discussed.
U.S. Pat. No. 3,938,530 is directed to a retention-type catheter for drainage of a urinary bladder. This system is closest to the present invention insofar as its retention means consist of radially displaceable strips 11, defined by longitudinal and circumferentially spaced slits 10, which are displaced by foreshortening the catheter's proximal end. Unlike the present invention, the foreshortening is accomplished by sliding an inner secondary tube 6 within a primary tube 1, as illustrated in FIGS. 2, 3, 4. The use of a tube-within-a-tube system compromises the drainage catheter lumen and obstructs the drainage of urine. The urinary drainage system of this reference is both complex and expensive to manufacture.
U.S. Pat. No. 3,397,699 is directed at a retaining catheter having resiliently biased wing flanges, similar in certain ways to the present subject invention. The retaining flanges 4 are opened and closed by use of “ . . . a relatively stiff stylet 8 . . . ” (Column 3, lines 61-62) unlike the present subject catheter system. The problems and dangers associated with the use of a stylet are discussed above.
U.S. Pat. No. 4,575,371 is directed to a urinary catheter system with a retention member in the form of a reversibly expandable balloon. In this system, the expandable balloon is situated below the drainage inlet opening so that in its inflated condition a portion of the catheter tip projects past the balloon and prevents contact between the wall of the urinary bladder and catheter tip thereby minimizing infection and local tissue trauma. As may be seen in FIGS. 2-5, the retention balloon when fully expanded distends past the tip of the catheter. The embodiment of FIG. 5 reflects also that the retention balloon is bi-lobed with reversibly expandable balloon chambers 3′ and 3″ arranged on opposite sides of the catheter tube and which in their expanded condition project in front of the tip 2. This Patent system uses bowl-shaped balloons for retention of the urinary drainage catheter that prevents contact between the catheter tip and the bladder mucosa, thereby reducing or obviating infection and/or tissue trauma. In contradistinction to the present subject Patent system, this reference system provides for a catheter drainage hole above the retaining element, thus allowing residual urine to collect with the attendant risks of infection and bladder inflammation.
U.S. Pat. No. 3,108,595 is directed to a retention catheter system that is characterized by pre-formed mushroom-like tips that are either split or fenestrated so as to allow for the drainage of urine. This invention encompasses a catheter comprising an outer tube having one or more mushroom heads and an inner tube that is longitudinally slidable within the outer tube and serves both as a conduit for fluids as well as a means for reversibly extending the mushroom head. With reference to FIGS. 1-5 especially, the inner tube 12 can be slid longitudinally with respect to the outer tube 11 so as to cause the detent 23 to engage with a detent opening 26, at which time those portions 22 of the outer tube 11 are extended radially to provide a plurality of ring-like extensions 27 that serve to anchor or retain the catheter in the bladder, as well as to provide openings for bladder emptying. In the embodiments reflected in FIGS. and 8, drainage slots 59 are formed in the outer tube 53 and are arranged helically along the outer tube 53. Despite some similarities to the present subject Patent system, this reference system is a drainage tube with a sliding mechanism of action, designed to be inserted surgically, and inappropriate for transurethral placement.
Thus, there exists a need to replace the current indwelling urinary catheter balloon retention system with another system that is safer, less irritating and leaves essentially no residual urine.